The bad news is that it doesn't have a dedicated maintenance hatch, but the good news is that it shouldn't be too much faff getting inside. Here's a copy 'n' paste courtesy of notebookcheck.net:
The bottom cover of the IdeaPad 330S can be removed once all the
screws on the underside of the device are undone. After you remove the
bottom cover you will have access to the innards of the device. This
means that you will be able to clean the fan, replace the HDD or
change the battery. A black plate covers the entire motherboard, to
which it is secured by means of four screws. Once you remove this
plate you will be able to access the Optane unit and the RAM.
.......but just wasn't sure if optane could be upgraded.
If your laptop has 4GB of RAM then upgrade that. Optane is not a solution for systems crippled by insufficient RAM.
If you do want to upgrade the Optane module to a higher capacity one then that's fine but note that it's essential to disable it first so that the module can return its files back to the hard drive. If you simply remove it then your laptop will never boot.